Skull base tumors are a group of tumors that grow along different areas under the brain or within the bottom part of the skull. While most of the tumors are benign, due to their location, which is close to the brain and various nerves, their growth can cause significant problems. The most common types of these tumors in include glomus tumors, facial neuromas, schwannomas, chordomas, chondrosarcomas, and metastatic tumors, including head and neck cancers that spread to the skull base.
Glomus tumors are benign tumors that arise from the area behind the ear drum or from around the jugular vein (the vein that takes the blood from the brain to the heart). Rarely, these tumors can arise from the 10th cranial nerve (the vagus nerve). These tumors grow slowly and gradually can destroy the inner ear and other bone around them to involve the carotid artery (the artery that takes the blood to the brain) and even grow into the brain. If the tumor arises from the jugular vein, it may invade 3 of the cranial nerves (9, 10, and 11) and cause significant problems with swallowing and voice. Patients will generally present with gradual hearing loss, pulsatile whooshing sound in the ear, and nerve deficits. These tumors are generally vascular. Radiosurgery is a new modality of treatment for selected patients with glomus tumors. Radiosurgery is a non-invasive focused radiation technique to stop the growth of tumors. This method of treatment has been successful in treating over 90% of patients with glomus tumors.
Meningiomas can arise in the sphenoid bone and optic sheath. In the middle cranial base, meningiomas occur in the olfactory groove and planum tuberculum. Posterior fossa meningiomas include tumors of the petrous bone. Meningiomas can be divided into en plaque and en masse tumors. En plaque tumors are flatter and grow along the dura. En masse tumors bulge into the intracranial compartment and often have a dural tail on contrast-enhanced images from radiologic studies.
Schwannomas are tumors of the covering of nerves. They occur most commonly on the balance nerve and is called a vestibular schwannoma (also called an acoustic neuroma). The second most common intracranial schwannomas develop from the trigeminal nerve (the nerve that supplies the sensation to the face) and account for fewer than 8% of intracranial schwannomas. Trigeminal schwannomas usually arise from the root or ganglion and occupy the middle fossa and, sometimes, the posterior fossa. These schwannomas may occupy both the middle and posterior fossa with a dumbbell shape. Schwannomas of the other cranial nerves are rare, but include facial nerve schwannomas (facial neuroma), vagal schwannomas, among others.
Chordomas may develop at any age, but they present most commonly in persons aged 20-40 years and affect males more commonly. Chordomas develop from remnants embryonic tissues and are often outside of the dura (covering of the brain). Chordomas rarely spread to other areas, but they often invade structures around them. Because of its location (in front of the brainstem), approach to these tumors is complex. Approximately 10% of chordomas are malignant, which may be related to previous irradiation.
Chondrosarcomas are rare tumors of the skull base that grow slowly. Due to their involvement of the bony skull base, achieving full resection may require combined approaches to the skull base.
The symptoms are completely dependent on the size and location of the tumor. They range greatly from small periodic changes; such as headaches, dizziness or hearing changes, to much larger symptoms; such as a complete loss of vision and/or hearing, facial paralysis, or diminished cognitive function. Please consult our physicians if your present symptoms are staying the same or worsening, as nearly any symptom can be a result of a tumor. Only through a thorough evaluation by the physician and appropriate diagnostic tests can this be effectively evaluated.
Diagnosis of skull base tumors requires a careful history and physical examination. A CT and/or MRI scan may be performed to define the extent of these tumors. Additional testing may include: hearing and balance testing among others.
The Skull Base Surgery team at UC Irvine use minimally invasive approaches for certain skull base tumors including endoscopic approaches when indicated, computer-based image guidance, lasers for tumor removal, ultrasound removal of bone and tumor, and intra-operative MRI when indicated. Other types of tumors, sizes of tumors, or their location dictates a more invasive surgery. Further treatment can include radiation therapy and or stereotactic radiosurgery, which is performed by members of the skull base surgery team.
The Team Approach to the treatment of skull base tumors has become the best approach in the treatment of these complex disorders. The team involves a head and neck skull base surgeon (neurotologist or anterior skull base surgeon) and a skull base neurosurgeon. The combination of the two specialties allows for the best care for the patients. The Skull Base Surgery Team at UC Irvine discusses the plan of treatment for the patients and plans for the best option for each particular patient. The team also reviews imaging studies for patients from outside of Southern California before their visit and accommodates these patients to give them the best possible and most efficient care.
Computer-assisted imaging navigation has allowed for better identification and preservation of sensitive structures during surgery of skull base tumors. Using this technology, the surgeons can visualize on the screen in 3 dimensions where a particular tumor and its surrounding structures are located while performing the surgery to reduce the chance of complications. Computer-assisted image guidance navigation is a routine part of the skull base team's approach to skull base tumors.
Another area of cutting edge technology available at the UC Irvine Skull Base Program is the use of imaging during the surgery to insure that the entire tumor has been removed. The special intra-operative MRI suite allows the skull base surgeons to obtain an MRI during the surgery to see if the entire tumor has been removed. The patient will generally have an MRI at the beginning of the surgery and one after removal of the tumor. This ensures that the entire tumor was removed. If there appears to be some tumor left, the surgeon will know exactly where it is based on the MRI and can remove it quickly. UC Irvine skull base surgery is one of a few programs in the West Coast to have the capability of intra-operative MRI, which is a must for complex tumors.
The skull base surgery team at UC Irvine routinely uses endoscopes to visualize areas that are hidden and to remove tumors in various surgeries of the skull base. This allows for a minimally invasive approach to selected tumors in the skull base to reduce the time and extent of the surgery. The use of endoscopes for skull base surgery is "must" for selecting a team for the treatment of your complex skull base tumor. Exclusively endoscopic approaches for anterior skull base tumors are used routinely, but in posterior skull base tumors, a completely endoscopic approach is not advisable given the potential issues with bleeding.
Radiosurgery is a method of treating tumors of the skull base using radiation given from multiple different directions. The radiation gets concentrated on the tumor, but the surrounding normal brain gets significantly less radiation. It is a useful method for a selected group of patients with skull base tumors. Click here for more information on radiosurgery.
The skull base team at UC Irvine also is one of a handful of teams in the U.S., who in addition to using all 3 surgical approaches, also performs stereotactic radiation (radiosurgery) using both the new Perfection GammaKnife System as well as the CyberKnife System.
Ultrasonic bone removal is a novel device that is used for removal of bone in critical areas around the brain or cranial nerves. Instead of using a high speed drill around the structures of the brain, this device can gently remove bone without the risk to the surrounding structures. The surgeons at UC Irvine use the ultrasonic bone removal system in appropriate cases to reduce injury to the brain, cranial nerves, and the vital structures of the skull base.
Another novel set of instruments used in the removal of skull base tumors is the stimulating dissection instruments. Traditionally, tumors were removed with various instruments and then a stimulator was brought into the field to check for the location of the important nerves in the area. The problem with that system was that the nerves (such as the facial nerve) could be injured while removing the tumor. The stimulating dissection instruments give the surgeon the ability to continually stimulate and look for the nerve as the dissection continues. This allows for maximal preservation of the nerve. The stimulating dissection instruments are used in the removal of all tumors of the posterior and middle skull base at UC Irvine.
Our center has been successful in having superb facial nerve function after removal of large tumors (over 3 cm) by using novel techniques using stimulating dissection instruments and occasionally combining surgical resection with post-operative radiosurgery. The use of newer technology allows the surgeons to preserve hearing and facial nerve at a higher rate.
Reconstruction of complex defects of the skull base is another challenge in the treatment of these disorders. Since these tumors are generally in difficult to reach locations close to the brain, the ability to stop the leakage of spinal fluid and stopping the communication of the brain with the nose, mouth, or the ear is important. Dr. Jason Kim, who is a full-time member of the UC Irvine Skull Base Team, specializes in anterior skull base surgery and in microvascular free flaps for the repair and reconstruction of these complex defects.
To Make an Appointment at the UC Irvine Skull Base Center, Please call 714-456-7017 or click here to request an appointment via the web.